Does finasteride (Propecia) affect male fertility?

Finasteride's Impact on Male Fertility

Finasteride can negatively affect male fertility, with documented cases of decreased ejaculate volume, reduced sperm parameters, and reports of male infertility that typically improve after discontinuation of the medication. 1

Effects on Fertility Parameters

Finasteride, a 5-alpha reductase inhibitor commonly used to treat benign prostatic hyperplasia (BPH) and androgenetic alopecia, has several documented effects on male reproductive parameters:

• Semen volume changes: Treatment with finasteride for 24 weeks causes a 0.6 mL (22.1%) median decrease in ejaculate volume with a concomitant reduction in total sperm per ejaculate 1
• Reversibility: These parameters typically remain within normal range and are reversible upon discontinuation of therapy, with an average time to return to baseline of 84 weeks 1
• Post-marketing reports: There have been documented cases of male infertility and poor seminal quality associated with finasteride use, with normalization or improvement after discontinuation 1

Clinical Evidence and Case Reports

Several studies have documented the effects of finasteride on male fertility:

• Case reports show that men with pre-existing subfertility or impaired spermatogenesis may be more vulnerable to finasteride's effects 2, 3
• In one case, a patient with azoospermia who had been taking finasteride 1mg for androgenic alopecia showed improvement in semen volume immediately after cessation, with sperm concentration increasing to more than 10 × 10^6/mL 16 weeks after stopping the medication 2
• Another case documented secondary infertility after prolonged use of low-dose finasteride, with improvement in semen parameters and sperm DNA fragmentation index after discontinuation, resulting in pregnancy and live birth 3

Contrasting Evidence

Some studies show minimal effects in healthy men:

• A double-blind, placebo-controlled multicenter study of 181 young men (19-41 years) found no significant effects of 1mg finasteride daily on sperm concentration, total sperm per ejaculate, sperm motility, or morphology after 48 weeks of treatment 4
• The same study noted only a small decrease in ejaculate volume (-11%) compared to placebo (-8%), with a median between-treatment group difference of -0.03 mL 4

Mechanism of Action and Reproductive Impact

Finasteride works by inhibiting the 5-alpha reductase enzyme:

• It selectively inhibits the 5-AR type II isoenzyme, reducing serum levels of dihydrotestosterone (DHT) by approximately 70% 5
• Animal studies suggest finasteride can act as a hormone disruptor, causing oxidative stress and morphological changes primarily in the testis 6
• Comparative studies indicate finasteride may be more harmful to male reproductive health than other treatments like minoxidil, as it's more associated with reproductive injuries including damage to the epididymis, erectile dysfunction, decreased libido, and reduced semen volume 6

Clinical Recommendations

For men concerned about fertility while using finasteride:

1. Fertility planning: Men planning pregnancy should be informed about the potential effects of finasteride on fertility parameters 7

2. Discontinuation timing: Consider stopping finasteride before attempting conception, as parameters typically improve after discontinuation 1, 2, 3

3. Monitoring: For men with pre-existing subfertility who require finasteride, close monitoring of semen parameters is advisable 2

4. Reassessment: If conception is not achieved within 6-12 months or if semen parameters decline significantly, consider assisted reproductive technologies 7

Important Caveats

• Men with pre-existing subfertility or impaired spermatogenesis may be more susceptible to finasteride's effects on fertility 2
• The effects appear to be reversible in most cases after discontinuation 1
• Patients should be counseled that while there are documented cases of successful pregnancy after finasteride discontinuation 8, the drug may temporarily impact fertility parameters

For men taking finasteride who are planning to conceive, discontinuation of the medication should be considered, with the understanding that improvement in semen parameters typically occurs within several weeks to months after stopping the drug.